linux-kernel - Re: [PATCH] tpm: Wrap the buffer from the caller to tpm_buf in tpm

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Message-ID: <20190917191307.GH10244@linux.intel.com>
Date:   Tue, 17 Sep 2019 22:13:07 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     linux-integrity@...r.kernel.org, Mimi Zohar <zohar@...ux.ibm.com>,
        stable@...r.kernel.org, Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: Wrap the buffer from the caller to tpm_buf in
 tpm_send()

On Mon, Sep 16, 2019 at 02:04:54PM -0700, Jerry Snitselaar wrote:
> On Mon Sep 16 19, Jerry Snitselaar wrote:
> > On Mon Sep 16 19, Jarkko Sakkinen wrote:
> > > tpm_send() does not give anymore the result back to the caller. This
> > > would require another memcpy(), which kind of tells that the whole
> > > approach is somewhat broken. Instead, as Mimi suggested, this commit
> > > just wraps the data to the tpm_buf, and thus the result will not go to
> > > the garbage.
> > > 
> > > Obviously this assumes from the caller that it passes large enough
> > > buffer, which makes the whole API somewhat broken because it could be
> > > different size than @buflen but since trusted keys is the only module
> > > using this API right now I think that this fix is sufficient for the
> > > moment.
> > > 
> > > In the near future the plan is to replace the parameters with a tpm_buf
> > > created by the caller.
> > > 
> > > Reported-by: Mimi Zohar <zohar@...ux.ibm.com>
> > > Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
> > > Cc: stable@...r.kernel.org
> > > Fixes: 412eb585587a ("use tpm_buf in tpm_transmit_cmd() as the IO parameter")
> > > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> > > ---
> > > drivers/char/tpm/tpm-interface.c | 8 ++------
> > > 1 file changed, 2 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > > index d9ace5480665..2459d36dd8cc 100644
> > > --- a/drivers/char/tpm/tpm-interface.c
> > > +++ b/drivers/char/tpm/tpm-interface.c
> > > @@ -358,13 +358,9 @@ int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen)
> > > 	if (!chip)
> > > 		return -ENODEV;
> > > 
> > > -	rc = tpm_buf_init(&buf, 0, 0);
> > > -	if (rc)
> > > -		goto out;
> > > -
> > > -	memcpy(buf.data, cmd, buflen);
> > > +	buf.data = cmd;
> > > 	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to a send a command");
> > > -	tpm_buf_destroy(&buf);
> > > +
> > > out:
> > > 	tpm_put_ops(chip);
> > > 	return rc;
> > > -- 
> > > 2.20.1
> > > 
> > 
> > Nothing uses the out label any longer so it should be dropped as well, but other than that...
> > 
> > Acked-by: Jerry Snitselaar <jsnitsel@...hat.com>
> 
> sigh (wrong emacs macro hit), that should be:
> 
> Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>

Thank you! I pushed the commit to master/next.

/Jarkko